This invention relates to a scanning tunneling microscope.
FIG. 2 shows an example of conventional STM apparatuses. A fine movement element block 1 having the construction wherein a probe 102 is disposed at the end portion of a fine movement element 101 is fitted into a cylindrical member 11 slidably in the axial direction of the cylinder. The fine movement element 101 can extend and contract in a Z-direction (in the axial direction of the fine movement element 101) or can be bent in X-Y direction by electrical stimulus.
A rough feed mechanism 10 consists substantially of a step motor 12 and a feed screw 13 connected to the output shaft of this motor. The feed screw 13 is fitted to the fine movement element block 1. Accordingly, where the feed screw 13 of the rough feed mechanism 10 rotates, the fine movement element block 1 is moved in the axial direction with respect to the cylindrical member 11.
A sample 5 is held by a sample holder 51, which is fitted and fixed to the front end surface of the cylindrical member 11.
To measure the sample by the probe, therefore, the fine movement element block 1 is fed roughly in the sample direction while the fine movement element 101 is being driven and rough movement is stopped at a position where a tunnel current is detected. Next, the fine moving element 101 is driven in the inner plane direction of the sample to make measurement. In this manner, rough movement, fine movement and the sample are integrated with one another in accordance with the prior art technique.
The STM apparatus is an apparatus which has resolution of an atomic level. Recently, the use of the STM apparatus for the observation of fine surface shapes in a micron meter range has been started. Though having high resolution, the STM apparatus is also characterized in that its maximum observation range is as narrow as about 10 .mu.m. It is therefore extremely difficult to locate the observation range to the place of a sample to be observed (such as a scratch) by use of the STM apparatus alone. Even in an STM apparatus equipped with a precision sample moving table (e.g. "Development of STM Apparatus Equipped with Sample Moving Stage", Technical Paper of Fall Meeting of '88 Precision Engineering Society, pp. 907), rough positioning is made from an obliquely transverse direction and STM measurement is repeated by moving finely the sample by the precision moving table in order to make positioning on the trial-and-error basis. It has therefore become necessary to position a desired measurement position of the sample by optical observation means and then to position the STM measurement area to this position.